The U.S. Embassy is advising travelers to exercise caution in Haiti after four U.S.
citizens were killed in separate robberies near Port-au-Prince's airport.

All those killed were visiting relatives in
Haiti, embassy officials told
The Associated Press on Monday. The attacks occurred over three months
and in three different locations.

The warning comes as scores of Americans are streaming
in to provide post-earthquake aid and help with reconstruction. It says
authorities believe criminals may be targeting travelers arriving from the United States and
advises caution in arrangingtransport from the
airport.

Haitian police spokesman Frantz Lerebours said he
had no information about the attacks.

Some worry the warning could hamper efforts
to court investment to rebuild Haiti's once-viable tourism sector in
hopes of reviving the impoverished
country's moribund economy.

Crime rates are high across the Caribbean,
including countries still known as tourism hotspots. Jamaica has the region's highest murder
rate; this month the U.S. Embassy in Kingston advised visitors to be on
alert for gang violence there.